2 NEW relays in parallel would provide twice the contact area, therefore dropping the amp load on a given set to 1/2 of what it was.
In this way, I don't think we would ever see the contact erosion problems currently being experienced.

That being said, I am inclined to think that the best solution would be to use a 100 amp relay driven by the existing relay.
( or remove the existing relay and wire in the larger one )
This : Sales Hot Car Motor Automotive 12V 100A 100 Amp SPST Relay 5 Pin 5P Heavy Duty | eBay or
http://www.grainger.com/product/GRAI...AS01?$smthumb$ ( 70 amp, but much better than the current 40 amp one )
may even fit inside the RCM so no external wiring would need to be done.